IN THE THICK OF CIVIL WAR A COURAGEOUS DOCTOR FROM IDAHO BEATS BACK AN EPIDEMIC BY LAUNCHING A

Aviation maps list Duar, a sprawling agglomeration of African huts, as Dwil Keil--the "lone house." In retrospect, the description sounds ominously prophetic. Located in south Sudan's western Upper Nile region, Duar found itself at the epicenter of a deadly epidemic--one of the least publicized to hit Africa in recent decades--that raged through the late 1980s and the 1990s. Of Duar's more than 1,000 original inhabitants, only four were left alive. The epidemic also took the lives of more than 100,000 people in the surrounding region.

The cause of this destruction was kala-azar (scientifically known as visceral leishmaniasis), a deadly disease caused...